If you're interested in the 'cracks' with regards to NDEs, definitely read The Spirit Molecule by Rick Strassman. That book, along with a few Terence McKenna lectures, will destroy any last vestiges of a materialistic worldview.
(To learn more about Terence McKenna, start with these:
It's always healthy to be versed with the opposing viewpoint, so I'd suggest reading How the Mind Works by Steven Pinker for a well articulated and evidenced materialistic thesis.